The present invention relates to a semiconductor integrated circuit device having fuses, and more particularly to a semiconductor integrated circuit device which is capable of preventing each of internal circuits from being broken due to a surge current generated when a certain fuse is blown.
In a semiconductor integrated circuit device, for example, a memory device such as a DRAM or an SRAM, a fuse is used for the purpose of rearranging a wiring of a redundant circuit for relieving a defective bit in a post-process after completion of a function test. A method of blowing a fuse by applying an excessive current, a laser beam or the like to a part of a wiring layer is adopted for a fuse element provided in the semiconductor integrated circuit device. When the fuse is blown with the Joule heat due to the excessive current, the excessive current itself may break each of the internal circuits. In addition, when the fuse is blown with the laser beam, it is thought that the surge current or the like generated by charge-up due to radiation of a light beam or thermoelectronic emission, or electro static discharge (ESD) accompanying generation or the like of an intra-surface potential distribution of a wafer due to a plasma gas generated in a phase of radiation of the laser beam to the fuse may cause the breaking of each of the internal circuits.
For example, a semiconductor integrated circuit device having a gate separation type diode as a protective element is known as a conventional semiconductor integrated circuit device which can protect each of internal circuits from the above-mentioned surge current or the like. In this semiconductor integrated circuit device, a fuse is provided in the middle of a wiring through which an internal circuit is connected to a grounding potential VSS. Also, the wiring through which the internal circuit and the fuse are connected to each other has a first gate separation type diode connected in a forward direction to a power supply potential VDD, and a second gate separation type diode connected in a forward direction to the grounding potential VSS. With the circuit structure described above, when a surge current having a polarity that it is caused to flow into the internal circuit is generated, the first gate separation type diode operates, while when a surge current having a polarity opposite to that polarity is generated, the second gate separation type diode operates, thereby protecting the internal circuit from the surge current. This semiconductor integrated circuit device, for example, is disclosed in U.S. Pat. No. 6,762,918.
However, the conventional semiconductor integrated circuit device as described above requires two or more protective elements per one fuse. In addition, there is encountered a problem about a responsibility to the surge current changing for a short period of time, accumulation of the electric charges due to the surge current, and the like. Thus, the conventional semiconductor integrated circuit device as described above does not have the reliability enough to protect the internal circuit from the surge current.